1. Field of the Invention
Apparatuses consistent with the present invention relate to a perpendicular magnetic recording head, and more particularly, to a perpendicular magnetic recording head in which a magnetic material is formed to control the magnetization direction of a soft magnetic underlayer of a perpendicular magnetic recording medium.
2. Description of the Related Art
With the advent of the Information Age, the amount of digital information that a person or organization deals with has significantly increased. For example, many people use computers that have high data processing speeds and large information storage capacities to access the Internet and obtain various pieces of information. Central processing unit (CPU) chips and computer peripheral units have been improved to enhance the speed of data processing in computers, and various types of high density information storage media like hard disks are being developed to enhance data storage capabilities of computers.
Recently, various types of recording media have been introduced. Most of the recording media use a magnetic layer as a data recording layer. Data recording types for magnetic recording media can be classified into longitudinal magnetic recording and perpendicular magnetic recording.
In longitudinal magnetic recording, data is recorded using the parallel alignment of the magnetization of the magnetic layer on a surface of the magnetic layer. In perpendicular magnetic recording, data is recorded using the perpendicular alignment of the magnetization of the magnetic layer on a surface of the magnetic layer. From the perspective of data recording density, the perpendicular magnetic recording is more advantageous than the longitudinal magnetic recording.
FIG. 1A is a cross-sectional view of a conventional perpendicular magnetic recording head. Referring to FIG. 1A, the conventional magnetic recording head includes a perpendicular magnetic recording medium 10, a write head 100 writing data on the recording medium 10, and a read head 110 reading data from the perpendicular magnetic recording medium 10.
The write head 100 includes a main pole P1, a return pole P2, and a coil C. The main pole P1 and the return pole P2 may be formed of a magnetic material, e.g., NiFe, and may have different coercivities due to different compositions. The main pole P1 and the return pole P2 are directly used to write data on a recording layer 13 of the perpendicular magnetic recording medium 10. An auxiliary pole 101 may be formed on a side of the main pole P1 to concentrate the magnetic field generated in the main pole P1 while data is recorded in a selected region of the perpendicular magnetic recording medium 10. The coil C surrounds the main pole P1 and generates a magnetic field.
The read head 110 includes first and second magnetic shield layers S1 and S2 and a data reading magnetoresistance device 111 positioned between the first and second magnetic shield layers S1 and S2. While data is read from a predetermined area of a selected track, the first and second shield layers S1 and S2 shield the magnetic field generated by magnetic elements near the magnetoresistance device 111 from affecting the predetermined area. The data reading magnetoresistance device 111 may be a giant magnetoresistance (GMR) device or a tunneling magnetoresistance (TMR) device.
FIG. 1B is an enlarged view of portion A of FIG. 1A. A method of recording information on the perpendicular magnetic recording medium 10 will now be explained with reference to FIG. 1B. The magnetic field applied from the main pole P1 due to the coil C magnetizes the recording layer 13 in a perpendicular Z-axis direction to record data. The magnetic field passes through an intermediate layer 12 and a soft magnetic underlayer 11 and returns to the return pole P2. The perpendicular magnetic recording medium 10 travels in an X-axis direction continuously having information recorded on a predetermined track. Magnetic domains with independent magnetization directions are formed in the soft magnetic underlayer 11 made of a magnetic material. The magnetic field applied from the main pole P1 and passing through the soft magnetic underlayer 11 affects the magnetic domains of the soft magnetic underlayer 11 thereby changing the magnetization directions thereof. After data is recorded on the recording layer 13, the magnetic domains with the changed magnetization directions in the soft magnetic underlayer 11 may change the magnetization directions of magnetic domains in the recording layer 13. In this case, the data retention characteristics of the recording layer 13 are degraded. Furthermore, the changed magnetization direction of the domains in the soft magnetic underlayer 11 leads to formation of magnetic domain walls. And such kind of domain walls formation is highly undesirable since it generate magnetic noise signal during the reading process.
Accordingly, there is an attempt to fix the magnetization direction of the soft magnetic underlayer 11 by forming an antiferromagnetic layer made of IrMn, a ferromagnetic layer made of NiFe, and a spacer layer made of Ru under the soft magnetic underlayer 11. However, such an attempt increases the thickness of the perpendicular magnetic recording medium 10, thereby increasing the thickness of a storage medium using multi-layered disks and complicating manufacturing processes. This also increases the manufacturing cost and complexity. Also, since the coupling constant between the ferromagnetic layer and the soft magnetic underlayer 11 is small, it is difficult to fix the magnetization direction of the soft magnetic underlayer 11.